Tower-type strip annealing furnace



March 1940- A. G. HOTCHKISS TOWER-TYPE STRIP ANNEALING' FURNACE Filed NOV. 18, 1939 Inventor. Allefi G. Hotchkiss, b F a y 1235 Attorney.

Patented Mar. 26, 1940 UNITED STATES TOWER-TYPE STRIP ANNEALING FURNACE Allen G. Hotchkiss, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application November 18, 1939, Serial No. 305,111

Claims.

My invention relates to strip annealing furnaces of the tower-type such, for example, as that disclosed in the Otis patent, No. 2,181,738, issued Nov. 28, 1939. It has been found that under certain circumstances with a furnace of the type dis- 5 chamber. the more highly heated one, into the other. Such a flow has been observed even though the opening in the center partition of the furnace walls was completely closed.

It is the object of my invention to provide an improved furnace of the above mentioned type wherein the rapid exchange of heat between the chambers due to air or gas movement may be avoided, thereby facilitating temperature control of the cooler chamber.

My invention will be better understood from the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims.

Referring to the drawing, Fig. 1 is a vertical cross-sectional view of a tower-type furnace illustrating one embodiment of my invention, and Fig. 2 is a detail view of a similar furnace illustrating a modified form of my invention.

Inasmuch as the furnace to which my invention is applied is, for the most part, similar to that described by the above mentioned Otis patent, I shall limit the description herein to those features of the furnace which involve my invention. As in the patent, the strip 1 of material being heattreated enters the furnace at the bottom thereof, passes under the roll 2, then upward through the heating chamber 3, over the roll 4, down through the heating chamber 5, and finally under the roll 6 to cooling apparatus not shown. The heating chambers 3 and 5 are shown by way of examples heated by the resistance heaters I whereby the chambers are raised to the desired temperature which, for example, may be 1300 F. and 1800-F. respectively. The construction which I have provided differs from that shown by the aforementioned Otis patent in that the partition 8 separating the two chambers 3 and 5 extends approximately only through the upper half of the furnace, and at the lower end of this partition is the horizontal partition 9. By eliminating the vertical partition 8 through the lower portion of the furnace, heat exchange between the relatively cool entering strip and the hot leaving strip can take place more rapidly and hence there results a more efficient heating and cooling of the strip. The openings in the horizontal partition 9 must be made wider than that required merely to provide adequate clearance for the moving strip since they must be large enough to permit a workman to pass therethrough in order to inspect or renew heating units in the chambers 3 and 5. Moreover, it is advisable to have these openings relatively wide in order that the strip, in the event of breakage thereof, may not bunch up in the chambers but drop freely therethrough into the lower portion of the furnace. Since the lower part of the furnace comprises a single chamber the strip opening at the bottom may be as large as desired.

As pointed out above the unbalance of pressures in the two heating chambers gives rise to a flow of the heated gas (hereinafter used in the sense of air, a gas, or a combination of gases) from the chamber 5 through the strip openings at the top of the furnace into the chamber 3. To oppose or overcome this exchange of gas between the two chambers, I have provided means which will now be described to effect a partial'if not complete balance in the pressures in the two heating chambers. The means which I have devised and which are shown by Fig. 1 comprise the blower l2, shown as driven by the motor l3, having its intake connected through the pipe H with the opening l5, which is represented by way of example as being located directly below the chamber 5. The outlet of the blower connects through'the pipes l6 and I! with the headers l8 and I9 located adjacent the opening in the partition 9 for the entering portion of the strip. Each header is provided with a row of openings 'or a slot by which the gas delivered by the blower is expelled in jets directed upwardly and toward the strip. The amount of gas thus blown inwardly of the chamber and against the strip will be regulated by the speed of the driving motor or by a suitable damper illustrated at 20 in the delivery pipe or jointly byboth the motor and the damper. Preferably the amount of gas expelled by the jets in the headers will be just suflicient to counter-balance the difference in pressure at the bottoms of the two heating chambers, although an exact equalization of the pressures in the two chambers may not be desirable in all cases. in fact under certain conditions I may desire to have the jets cause a flow in the reverse direction to that which would naturally take place.

In the modified form of my invention illustrated by Fig. 2 the headers containing the jets are indicated at 2| and 22 and are located at the upper portion of the heating chamber 32, being arranged upon either side of the opening through which the strip passes to the roll 4. The jets, as in Fig. 1, are directed upwardly and toward the strip to prevent the flow of gas from chamber into chamber 3. In this case the intake to the blower is shown connecting with the chamber 23 in which the roll 4 is mounted. However, if desired, the inlet may connect with the upper part of the chamber 5. As in Fig. 1, the force of the gas ejected by the jets preferably is such as to prevent any material fiow of gas from chamber 5 into chamber 3 by way of the openings for the strip.

I have shown the particular embodiments described above as illustrative of my invention and it will be apparent that various other modifications may be made without departing from the spirit and scope of my invention, which modification-s I aim to cover by the appended claims.

What I claim as new and desire to secure by Letters Patent in the United States is:

1. A tower-type annealing furnace having a plurality of vertically disposed heat-treating chambers, a passage interconnecting said chambers at their upper ends and outwardly opening passages at the lower ends of said chambers, means for supporting a. strip of material to be heat-treated for movement through said chambers and passages, means for heating one of said chambers to a higher temperature than that of the other whereby unequal gas pressures occur in the chambers, and means comprising a gas blast for opposing the flow of gas from one chamber to the other due to said unequal gas pressures.

2. A tower-type annealing furnace having a plurality of vertically disposed heat-treating chambers, a passage interconnecting said chambers at their upper ends and outwardly opening passages at the lower ends of said chambers, means for supporting a strip of material to be heat-treated for movement through said chambers and passages, means for heating one of said chambers to a higher temperature than that of the other whereby unequal gas pressures occur in the chambers, and means for directing a blast of gas toward the strip and across one of said passages to prevent the interchange of gas between the chambers.

3. A tower-type annealing furnace having a plurality of vertically disposed heat-treating chambers, a passage interconnecting said chambers at their upper ends and outwardly opening passages at the lower ends of said chambers, means for supporting a strip of material to be heat-treated for movement through said chambers and passages, means for heating one of said chambers to a higher temperature than that of the other whereby unequal gas pressures occur in the chambers, and a nozzle arranged at each side of said. strip at one of said passages for directing blasts against the strip in a direction substantially to neutralize the eifect of said unequal gas pressures.

4. A tower-type annealing furnace having a plurality of .vertically disposed heat-treating chambers, a passage interconnecting said chambers at their upper ends and outwardly opening passages at the lower ends of said chambers, means for supporting a strip of material to be heat-treated for movement through said chambers and passages, means for heating one of said chambers to a higher temperature than that of the other whereby unequal gas pressures occur in the chambers, and a nozzle arranged on each side of said strip at the outwardly opening passage of one of said chambers for directing blasts against the strip and inclined inwardly of the passage.

5. A tower-type annealing furnace having a plurality of vertically disposed heat-treating chambers, a passage interconnecting said chambers at their upper .ends and outwardly opening passages at the lower ends of said chambers, means for supporting a strip of material to be heat-treated for movement through said chambers and passages, means for heating one of said chambers to a higher temperature than that of the other whereby unequal gas pressures occur in the chambers, and a nozzle arranged at each side of said strip at said interconnecting passage for directing blasts against the strip and inclined thereto for opposing a flow of gas from one chamher to the other due to said unequal pressures.

- ALLEN G. HOTCI-IEESS. 

